Conditions for Universe's First Stars Recreated In Lab

The first primordial stars began as tiny seeds that grew rapidly into stars one hundred times the mass of our own Sun. Seen here in this artist impression, swirling clouds of hydrogen and helium gasses are illuminated by the first starlight to shine in the Universe.Credit: David A. Aguilar (CfA)

About 13.7 billion years ago, the Big
Bang is thought to have created our universe. For about 1.5 billion years,
the universe went through a cosmic dark age, until finally the first stars and galaxies
were born.

Many details of how those stars were born are not known, but
the new experiment helps fill in some gaps.

"The first star
formation is a really fascinating intersection between chemistry and
cosmology," said researcher Daniel Savin of Columbia University in New
York, during a Wednesday press conference. "What it's telling us is that
in order to understand the very beginnings of star formation, we need to really
understand fundamental chemistry."

Early universe unveiled

The early
universe was made mostly of hydrogen, with some helium and trace amounts of
other elements. This matter clumped together under its own gravitational pull
to form clouds.

Within these clouds, scientists think hydrogen atoms (which
contain one proton and one electron) bonded with negatively charged hydrogen
ions (one proton and two electrons) to form molecular hydrogen, consisting of
two hydrogen atoms chemically bonded. This chemical reaction served to cool and
condense the clouds until they were dense enough to ignite nuclear fusion, the
process that powers stars.

Theorists had predicted this chemical reaction, but had
trouble calculating just how it would happen and how quickly.

Recreating star formation on Earth

The researchers, led by Columbia astrophysicist Holger
Kreckel, succeeded in recreating the reaction in the lab. The scientists
created a beam of hydrogen atoms and a beam of hydrogen ions and merged them
together to create hydrogen molecules. They were able to precisely tune the
velocities of the beams to calculate how changing their collision energy would
affect how quickly the reaction took place.

Finally, the researchers compared their findings to
theoretical predictions to constrain estimates of how massive the
first stars likely were.

"We can say with a much higher degree of confidence
whether a primordial cloud will actually form a star," Savin said.

The team reported their findings in the July 2 issue of the
journal Science.